Felt for papermaking machine

ABSTRACT

A FELT FOR USE IN A PAPERMAKING MACHINE INCLUDING AN ENDLESS BELT ON THE BACK SIDE OF WHICH A PLURALITY OF MONOFILAMENTS ARE ADHERED IN SPACED RELATION, THE MONOFILAMENTS DEFINING WATER-CONVEYING CHANNELS INTO WHICH WATER EXPRESSED FROM A PAPER SHEET LOCATED ON THE FACE OF THE BELT IS DIRECTED WHEN THE ENDLESS BELT AND THE PAPER SHEET ARE MOVED THROUGH A PRESS SECTION OF THE PAPERMAKING MACHINE

1 .4. nn-mm u 0a. 19, 1971 A E O 3,613,258

FELT FOR PAPERMAKING MACHINE Filed Sept. 15, 1969 2 Sheets-Sheac 1(Hwymul /mu, ,0

30 I i d 6 m 0. I, 12 k lld 4 Inventor; ThomasA.

Jamz'esorz,

Aug s.

o 19, 1971 T- A. JAMIESON 3,613,253

FELT FOR PAPERMAKING MACHINE med Sept. 15, 1969 2 Sheets-Sheet 2 mm zmmuw:

y/azzo 1M Atg s.

Unlted States Patent O Int. Cl. F26b 13/26 US. Cl. 34-95 12 ClaimsABSTRACT OF THE DISCLOSURE A felt for use in a papermaking machineincluding an endless belt on the back side of which a plurality ofmonofilaments are adhered in spaced relation, the monofilaments definingwater-conveying channels into which water expressed from a paper sheetlocated on the face of the belt is directed when the endless belt andthe paper sheet are moved through a press section of the papermakingmachine.

BACKGROUND OF THE INVENTION The present invention has particularapplication in papermaking machines and provides for the effectiveremoval of water from a paper sheet as the paper sheet and felt on whichthe paper sheet is carried are directed into a press section of thepapermaking machine.

Normally water is removed from the paper sheet in two ways, that is,mechanically in a press section of the papermaking machine or byevaporation in a dryer section of the papermaking machine. The mostpractical solution for removing the water from the paper sheet is bypress removal as the sheet and felt are squeezed between rolls in thepress section. The felt in common use heretofore that carried the papersheet through the press section was formed so as to direct the water outof the sheet at the press nip, the water moving laterally through thefelt for dispersement thereof. In another type of press design, asuction area was located within one of the rolls at the press sectionand communicated with the press nip through a plurality of holes. Thewater was directed through the felt into the suction area through theholes and was received in the suction roll shell for dispersal.

Although the prior-known techniques for removing water from a papersheet were effective under certain conditions, it has been found inrecent times, with the improvement of papermaking machinery, that thespeed of the paper sheet as it is directed through the various sectionsof the machine produces problems in removing the water therefrom. Thus,because of the high speed of the rolls in the press sections, the waterwas not able to escape effectively and, as a result, it was necessary toreduce the speed of the paper making machinery so that sufficient timewas available for evaporation of the remaining water in the dryingsection. In some instances crushing occurred in the paper sheet unlesslower speeds were employed in movement of the paper sheet through thepapermaking machine.

Some efforts have been made to increase the rate of dispersal of thewater from the paper sheet at increased speeds of the papermakingmachinery and equipment known as a fabric press and a grooved press weredeveloped. In the fabric press, a relatively imcompressible syntheticfabric was placed under the felt and water that was squeezed out of thesheet and felt was received in the fabric rather than being squeezedbackwardly longitudinally through the felt. The water was stored in thefabric until the fabric had left the pressure area of the nip of thepress, at which time the water was thrown out or removed by vacuum. Inthe grooved press, a plurality of helical grooves were cut in one of thepress rolls, the grooves being vented to atmosphere on both sides of the3,613,258 Patented Oct. 19, 1971 nip. As the water was forced into thefelt on the nip section, the grooves provided a place for the expressedwater to enter and, since the grooves were vented to atmosphere, waterhandling capacity was not limited by groove size in the nip area.Although these prior-known systems did increase the water handlingcapacity of the felt as the felt and sheet moved through the presssection, they were still not totally effective in removing the waterfrom the felt when the equipment was moving at very high speeds.

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SUMMARY OF THE INVENTION The felt for use in a papermaking machine asembodied in the present invention is comprised of an endless belt thatis composed of a weave having warp and filling yarns or warp yarns only,the belt including a face for receiving a paper sheet in contacttherewith and a back side that defines the inside surface of the belt.In order to provide channels for conducting water that is expressed fromthe paper sheet in contact with the belt, a plurality of monofilamentsare located in spaced relation in contact with the back side of theendless belt. The monofilaments are preferably formed of a syntheticplastic material and are extruded in hot melt form so that when they areapplied to the back side of the endless belt they are permanentlyadhered thereto. The spacing of the monofilaments define a plurality ofchannels that preferably extend in the warp direction, and since themonofilaments are resistant to abrasion and can be effectively squeezedbetween the rolls in the nip section and still retain their shape sothat the water expressed from the paper sheet is effectively transferredthrough the channels to a dispersal area.

Accordingly, it is an object of the present invention to remove waterfrom a paper sheet before the paper sheet reaches the drying section sothat less drying by evaporation in the drying section is required.

Another object of the present invention is to provide a felt for use ina papermaking machine on the back surface of which a plurality ofmonofilaments are adhered in spaced relation to define water conveyingchannels.

Still another object of the invention is to provide a papermaking feltto the back of which a plurality of monofilaments, formed of a syntheticplastic material, are adhered to define a plurality of channels, thechannels forming water-conveying paths through which water expressedfrom a paper sheet carried by the felt is directed when the felt andpaper sheet are moved through a press section of a papermaking machine.

Still another object is to provide a felt for use in a papermakingmachine having monofilaments adhered to the back surface thereof todefine water-conveying channels, the monofilaments being formed of asynthetic plastic material and having a diameter in the range of.0l0.100.

Still another object is to provide a felt for use in a papermakingmachine that is formed in an endless belt and that is provided with abatt surface that is needled to the warp and filling yarns on both sidesthereof, a plurality of monofilaments being adhered directly to the battsurface on the back of the felt and defining water-conveying channelstherebetween.

Still another object is to provide a felt for use in a papermakingmachine wherein a plurality of monofilaments are extruded in hot meltform and applied to the back side of the felt for permanent securementthereto.

Other objects, features and advantages of the invention shall becomeapparent as the description thereof proceeds when considered inconnection with the accompanying illustrative drawing.

DESCRIPTION OF THE DRAWING In the drawing which illustrates the bestmode presently contemplated for carrying out the present invention:

FIG. 1 is a perspective view with portions broken away of thepapermaking felt embodied in the present invention;

FIG. 2 is a fragmentary top plan view of the papermaking feltillustrated in FIG. 1;

FIG. 3 is a sectional view taken along line 33 in FIG. 2;

FIG. 4 is a view similar to FIG. 3 showing a modified form of theinvention; and

FIG. 5 is a view similar to FIG. 3 showing another modified form of theinvention.

DESCRIPTION OF THE INVENTION Referring now to the drawings, andparticularly to FIG. 1, the papermaking felt embodied in the presentinvention is generally indicated at and, as shown, is defined by anendless belt, the general construction of which may be formed in anyconventional manner. In this connection, a needled felt is preferredand, as shown in FIG. 3, the

needled felt 10 includes a base material defined by warp yarns 12 andfiller yarns 14 and 16. The warp and filler yarns are woven on a loom inany conventional manner and may be formed of any material normallyemployed in the manufacture of papermaking felts. It is contemplatedthat wool and suitable synthetic materials will be utilized as the warpand filler yarns; however, the materials that define these yarns and themanner of weaving thereof form no part of the present invention.

Following the conventional splicing or tubular weaving of the warp andfiller yarns 12, 14 and 16, the endless belt that defines the felt 10 isplaced on a conventional needling machine and the base materials thatdefine the weave have a non-woven batting material needled on one orboth sides thereof, as indicated at 18 and 20, the needled material 20defining the face of the felt and the needled material 18 defining theback side thereof. The batts that are needled into the base weave arenormally formed of a blend of wool and synthetic fibers on which asecond batt of woolen fibers are needled to form a finished surface. Itis understood, of course, that the batt material that defines thesurfaces of the felt may be formed of any conventional fibers, dependingupon the requirements of use of the felt. The number of layers of thebatt material as needled into the base weave will also be determined bythe end use of the felt.

As will be described, the felt 10, as embodied in the present invention,provides for the effective removal of water in the press section of thepapermaking machine. Water is usually removed from the felt in a presssection as the felt and sheet carried by the felt are squeezed betweenthe rolls that define the press nip, thus squeezing Water from the papersheet into the felt. Heretofore the felt carried the sheet through thepress section and the water that was squeezed out of the sheet at thenip was expelled through the felt either laterally in a plane press,

or into the grooves of a grooved press, or through holes drilled in ashell that had communication with a suction area in a suction press. Ithas been found that when the felt and sheet thereon are moved at highspeeds during the papermaking operation, prior-known techniques did notremove a sufficient amount of the water from the paper sheet. In orderto avoid the problems experienced heretofore in removing water from thepaper sheet, the present invention provides for the application of aplurality of monofilaments that are adhered to the back side of thefelt. Referring again to FIG. 3, the monofilaments are indicated at 22and, as shown, are formed of a synthetic plastic material and extend inthe warp direction of the endless belt that defines the felt 10. Bylocating the monofilaments 22 in the manner as illustrated, a pluralityof longitudinally extending channels 24 are defined that form waterconduits for conducting water expressed from the paper sheet and felt toa dispersal area as the paper sheet and felt are carried through thepress section of the papermaking machine.

The monofilaments 22- are adhered directly to the batt 18 on the backside of the felt and may be extruded in continuous form in theapplication thereof, the felt being turned inside-out as themonofilaments are applied thereto. In this connection, the monofilaments22 are preferably extruded in a hot melt condition and, as applied tothe back side of the felt, adhere directly thereto for permanentattachment. It is contemplated that the monofilaments, as extruded, willbe formed of a synthetic resin, examples of which are polyamids,polyesters, epoxies, polyethylenes, polypropylenes and vinyls. In theextruded form of the monofilament, which is applied to the back surfaceof the felt in molten condition, it is seen that the adhered area may besomewhat flattened as the molten material flows onto the felt. However,the general configuration of the monofilament is cylindrical and it iscontemplated that the diameter thereof will be in the range of .010 to.100 inch. Since the spacing of the mono-filaments 2.2 will determinethe channels 24 defined therebetween, this spacing is somewhat criticalin that the water-conducting channels must be capable of providing forrapid dispersal of water as it is expressed from the paper sheet andfelt, but the monofilaments must also be sufliciently close enough toavoid any marking on the paper sheet as carried by the felt. In thisconnection, it is contemplated that the spacing of the monofilamentswill be approximately .090 inch, but will vary in the range of 1 to 3times the diameter of the monofilament as applied to the back side ofthe felt. It is understood that the spacing of the monofilaments asshown in FIG. 1 is for illustration only, since the monofilaments inactual practice will be considerably closer together than thatillustrated. As previously mentioned, in the preferred form of theinvention, the portions of the monofilaments that engage the felt aresomewhat flattened, since the monofilaments are normally applied in hotmelt form; thus the tendency to produce marking will be lessened.

Although the described method of application of the monofilaments to theback side of the felt is by extruding the monofilaments in molten formthereon, it is also contemplated that preformed monofilament yarns canbe applied by a suitable adhesive; or a solvent can be employed forrendering the preformed monofilament tacky, whereafter the tackymonofilament is applied to the felt for permanently adhering themonofilament thereto.

It is further contemplated that the monofilaments be allowed topenetrate into the felt surface, and in order to accomplish this, thefelt itself is heated to a suflicient temperature, wherein the viscosityof the molten monofilament, as applied to the felt, is such that themonofilament will penetrate the felt. Thus the temperature of the feltis controlled so as to provide for penetration of the monofilaments intothe surface of the felt. The channels between the monofilaments arestill maintained and function to retain the water expressed from thepaper sheet as the felt and paper sheet are moved through the presssection of the papermaking machine. The temperature of the felt may bemaintained at approximately 325 F. to 400 F. to provide for penetrationof the monofilaments therein. In this connection, hot air may beemployed for heating the felt to the required temperature.

Regardless of the materials that are employed for producing thewater-conveying channels, the properties of the monofilament must beconsistent with the operation of the papermaking machine. In thisconnection, the monofilament embodied herein is resistant to abrasion toresist rubbing in the press section where the felt makes contact withthe nip rolls. The monofilament, as con templated for use in the presentinvention, also resists flattening during use, since the felt passesthrough the highpressure squeeze rolls and is subjected to a force ofbetween and 1100 pounds per linear inch. It is further noted that themonofilament cannot be completely fiat when squeezed, since filling thevoid spaces must be avoided. The monofilament, as employed herein, alsohas a high degree of stretch or elongation, since the press rollsnormally stretch the felt. It is also understood that a certain degreeof elongation of the monofilament is required, since the felt is drivenby rolls and the monofilament must bend around the rolls withoutseparation from the felt. Sufficient tensile strength of themonofilament is also required to withstand the stretch forces that areapplied to the felt as the felt extends around the rolls and passesbetween the press rolls.

Since the monofilament is continually subjected to a flow of watertherebetween, it has a high water resistance, that is, it resistssoftening or weakening or change upon exposure to water. During thepapermaking operation, the paper is subjected to various operationsinvolving chemical materials and therefore the monofilament ischemically resistant, and in particular is resistant to those chemicalsthat are normally applied to the felt during the papermaking operation.From the above, it is understood that the monofilament as applied to thefelt is permanently adhered to the surface of the felt and since itremains in position throughout the life of the felt, it forms anintegral part of the felt surface.

In operation of the felt to which the monofilaments 22 are permanentlyadhered, the felt and paper sheet carried thereby move through the presssection of the papermaking machine and water expressed from the papersheet into the felt is directed between the monofilaments 22 and intothe channels 24 where it is carried to a dispersal area for removal fromthe felt.

As illustrated in FIG. 3, the monofilaments 22 are attached to the battsection 18 that is adhered to the back side of the weave defined by thewarp threads 12 and the filling yarns 14 and 16. However, it iscontemplated that the monofilaments 22 may be adhered directly to thefiller yarns, and referring now to FIG. 4, a plurality of warp yarns 26are shown woven into filler yarns 28 and 30. The filler yarns 28 and 30cooperate with the warp yarns 26 to define a two-over, two-underconfiguration. The monofilaments 22 are directly adhered to the filleryarns 28 and 30 and normally extend in the warp direction. In the feltillustrated in FIG. 4, a batt 32 is needled into the warp and fillingyarns and defines the face of the felt. As described above, channels areformed between the monofilaments 22 and define water conducting pathsfor directing water expressed from the paper sheet to a dispersal area.As described herein, the monofilaments 22 are shown extending in thewarp direction, which is the preferable manner of locating themonofilaments in place on the back side of the felt. However, themonofilaments may be placed in angular relationship with respect to thewarp and filling yarns, or the monofilaments may be criss-crossed todefine double spaces, if it is so desired.

Referring to FIG. 5, a modified form of the felt is generallyillustrated at 34 and includes a needled felt defined by warp yarns 36and filler yarns 38 and 40 on both sides of which non-woven batting 42and 44 are needled. Fixed to the needled batting 44 on the reverse sideof the felt are a plurality of monofilaments 46 formed of a syntheticplastic material of the type mentioned hereinabove. The monofilaments 46are preferably applied in hot melt form and are adhered to the batting44 longitudinally thereof to define water conduits for conducting waterexpressed from the paper sheet carried by the felt as the paper sheetand felt are moved through the press section of the papermaking machine.In order to avoid any possibility of snagging or peeling of themonofilaments 46 as the felt 34 is moved through the press section, themonofilaments are covered by another batting layer 48 that is needleddirectly into the batting 44 and woven yarns 36 and 38. It is seen thatalthough the monofilaments 46 are covered by the outer batting 48, thechannels between the monofilament are clearly defined and will stillfunction to retain the water therein as the paper sheet and felt aremoved through the press section of the papermaking machine.

As described herein, the present invention provides a unique andeffective means for receiving and conducting water expressed through thepaper sheet and felt regardless of the speed of the felt as it is movedthrough the press section in the papermaking machine. Not only does themonofilament provide a novel means for insuring effective removal ofwater from the paper sheet, but it also renders the felt more wearresistant, thereby causing the felt to last longer in use. Thus the useof the monofilament provides for longevity of the felt.

What is claimed is:

1. A felt for use in a papermaking machine, comprising an endless beltcomposed of a base material, said belt including an outer face forreceiving a paper sheet in contact therewith and a back that defines theunderneath side of said belt, and a plurality of monofilaments fixed tothe outer surface of the back of the endless belt, said monofilamentsbeing disposed in spaced apart, parallel relation to define a pluralityof exposed, parallel spaced channels that are located directly on theouter surface of the back of the endless belt and that are generallyparallel to the direction of movement thereof, said channels beingrelatively free of fibers or yarns formed in the base material andforming water conveying paths through which water expressed from thepaper sheet is directed when said endless belt and paper are movedthrough a press section of the papermaking machine.

2. In a felt as set forth in claim 1, said monofilaments being formed ofa synthetic plastic material and being adhered to the outer surface ofthe back of the endless belt, said plastic material being relativelyincompressible so as to retain the structural integrity of the channelsas the felt and paper sheet travel through the press section of thepapermaking machine.

3. In a felt as set forth in claim 2, the synthetic plastic materialfrom which said monofilaments are formed being selected from the groupconsisting of polyarnrcie, polyester, epoxy, polypropylene polyethyleneand viny 4. In a felt as set forth in claim 2, said monofilaments beingextruded in hot melt form so that when they are applied to the back ofsaid endless belt, they are permanently adhered thereto.

5. In a felt as set forth in claim 2, the diameter of said monofilamentsbeing in the range of .O lO-JOO inch, and the spacing between themonofilaments being in the range of one to three times the diameter ofthe monofilaments.

6. In a felt as set forth in claim 1, said endless belt including a battsurface that is needled into the warp and filling yarns on both sidesthereof, said monofilaments being adhered directly to the batt surfaceon the back of said belt.

7. In a felt as set forth in claim 1, said endless belt including a battsurface that is needled into the Warp and filling yarns to define theface of said belt, said monofilaments being adhered directly to thefilling yarns on the back of said belt.

8. In a felt as set forth in claim 1, said monofilaments extendinggenerally in the warp direction.

9. In a felt as set forth in claim 8, said monofilaments being formed ofa synthetic plastic material and being extruded in hot melt form andapplied to the back of said endless belt for permanent adherencethereto.

10. In a felt as set forth in claim 9, the diameter of saidmonofilaments being the range of .010-.10O inch and the spacing betweenthe monofilaments being in the range of one to three times the diameterof the monofilaments.

11. In a felt as set forth in claim *9, a layer of batt materialoverlying said monofilaments on the back of the endless belt.

8 12. In a felt as set forth in claim 1, said felt being 3,325,9096/1967 Clark 34-95 heated to a temperature that provides for penetration3,401,467 9/1968 Koester 34-95 of said monofilaments into said felt onthe back side 3,437,538 4/1969 Ewing 156-181 X thereof.

Referen e Cit d 5 FREDERICK L. MATTESON, 111., Primary Examiner UNITEDSTATES PATENTS H. B. RAMEY, Assistant Examiner 2,738,298 3/1956 David atal. 156-181 X 3,097,413 7/1963 Draper 34-95 3,279,504 10/1966 Wagner34-95 10 161-150; 162-358

